1. Field of the Invention
The invention relates to an axial piston pump or motor, of the swashplate or bent axis type, wherein a fixed control plate, which comprises at least one control passage, consisting of a plurality of control passage sections separated from each other by bridges, is arranged between a cylinder drum, rotatable in both directions of rotation, and a fixed housing of the pump or motor.
2. Description of Related Art
Such an axial piston pump is described in German Patent DE 37 25 361 C2. In order to reduce the running noise the control plate of this known axial piston pump, in the transition regions between the control passages for the supply or removal of the operating fluid, that is to say the high pressure passage and the low pressure passage, comprises a pressure balancing passage, through which a relatively gentle adaptation of the cylinder pressures occurs, before the cylinder opening of the respective cylinder lies in the cross sectional region of the high pressure passage. During this operation a fluid jet which, due to jet erosion and cavitation erosion causes wear damage on the control passage walls and the control plate, passes through the pressure balancing passage. In order to prevent such erosion an interference passage is allocated to the pressure balancing passage, which produces an interference jet intersecting the fluid jet and thereby weakens this.
It has now been shown with axial piston pumps that also outside the transition area between the control passages for the supply and removal of the operating fluid, damage by cavitation can occur on structural part surfaces cooperating with the control plate, which cannot be prevented by a combination of a pressure balancing passage with an interference passage. In particular such erosion has been observed not only in the high pressure region, but also in the low pressure region.
With this as the starting point the object of the invention is to provide a control plate for an axial piston pump or motor which is designed in such a way that damage to structural parts is prevented over the entire extent of the control passages for the supply and removal of the operating fluid.